Wide-body connector for concrete sandwich walls

ABSTRACT

Wide-body connectors are provided for concrete sandwich walls. Each connector includes a body with longitudinally thickened portions defining flanges and a thinner inner connecting web extending between the flanges. The flanges provide increased bending stiffness for the connector, while the web provides enhanced shear transfer between the concrete layers of the wall. Anchoring surfaces are formed into or overmolded onto the body to anchor the ends of the connector in the concrete layers of the wall and assist in the creation of end moments ofr the transfer of forces between the concrete layers. Preferably, a lip is provided on the connector to limit the penetration of the connector through the insulation layer of the wall. The connectors transfer forces between the concrete layers, without thermal bridging, such that the wall has a substantially composite character.

BACKGROUND OF THE INVENTION

[0001] The invention relates generally to concrete sandwich walls and,more specifically to concrete sandwich walls wherein the two concretelayers are tied together by a plurality of insulating connectors thatare of a shape that provides significant shear transfer between the twoconcrete layers when the panel is subjected to forces applied normal tothe plane of the panel and at the same time reduces the number ofconnectors required to provide such stiffness. The concrete sandwichwalls are both stiff and strong while providing high thermal efficiency.

[0002] Insulated concrete sandwich walls are well known in the art.Typically, a concrete sandwich wall panel is created by installing alayer of insulating material between two layers of concrete. In order tocreate a safe assembly capable of resisting handling and service imposedforces, the insulation layer must be penetrated by a connection systemthat ties the two layers of concrete together.

[0003] Concrete sandwich wall panels can be constructed at the buildingsite or at a remote site and transported to the building site. Thepanels are constructed in a horizontal orientation and then picked ortilted to a vertical orientation for placement as a component of abuilding wall structure. A first layer of concrete is poured and leveledin the form. The layer of insulation is then placed on top of theplastic concrete and a plurality of connectors are inserted through theinsulation layer into the plastic concrete layer underneath. The secondlayer of concrete is then poured on top of the insulation layer.Accordingly, one end portion of the connectors is consolidated in thefirst concrete layer and the opposite end portion is consolidated in thesecond concrete layer. Upon setting of the concrete layers, theconnectors tie the two concrete layers together with the insulationlayer sandwiched therebetween.

[0004] Concrete sandwich wall panels clad the exterior of a building andmust resist lateral forces (wind and seismic forces), gravity loads, andtemperature-induced forces. Lateral forces as well as temperaturedifferentials between the two concrete layers induce shear forces in theconnection systems as well as bending, shear, and axial forces in bothlayers of concrete in the panel.

[0005] In the current art, sandwich panels are designed as composite,partially composite, or non-composite. A composite sandwich panel of agiven total thickness will have nearly the same stiffness and strengthas a solid panel of the same thickness, while a non-composite panel willhave roughly the same stiffness and strength as the sum of the stiffnessand strength values for the individual concrete layers comprising thewall panel. Partially composite walls will have stiffness and strengththat are intermediate to the values for composite and non-compositepanels.

[0006] Composite walls are normally constructed with steel trussespassing through the insulation. The steel trusses provide high shearstiffness and effectively limit differential slip between the concretelayers. These panels are therefore very efficient in resisting lateralloads. Unfortunately, these panels also have severely reduced insulationperformance as the steel trusses have high thermal conductivity andbridge the insulation.

[0007] Non-composite and partially composite wall panels are normallyconstructed using flexible connectors that are installed perpendicularto the plane of the insulation. Because the connectors provide low shearrestraint, large differential slip between the concrete layers ispossible. In the current art, partially composite panels are constructedby removing sections of insulation to provide discrete through-thicknessconcrete zones. These zones are normally located at the ends and atintermediate points along the length of the panel and limit the localslip between the concrete layers; however, the flexible connectorsbetween through-thickness concrete zones will allow local slip. Althoughthe uncracked stiffness of such panels will be nearly the same as for acomposite panel, partially composite panels will tend to crack at lowerloads than composite panels.

[0008] Although composite and partially composite walls are much moreefficient than non-composite walls in resisting normal horizontalforces, the connection system's enforcement of strain compatibilitybetween the concrete layers can create undesirable behaviors. Theprimary function of an insulated concrete sandwich panel is to provide athermal barrier between the ambient environment and the conditioned airwithin the building. The thermal barrier must, therefore, lead tosignificant temperature differentials between the two concrete layers.Consequentially, as one concrete layer increases in temperature, itexpands in the plane of the panel. The connection system and the otherconcrete layer eccentrically restrain this expansion, leading to“thermal bowing” of the assembly analogous to that observed with abi-metallic strip. Similar behavior will occur in composite or partiallycomposite panels with different levels of prestressing between the twolayers. While this can be primarily an aesthetic problem, it can alsolead to failure of the sealant at the joints between panels. This effectis most dramatic at the building corners, where the differentialmovement is magnified by the geometry of the joint. Also, in manyapplications, both composite and partially composite panels have excesscapacity.

[0009] In contrast to a composite wall connection system, anon-composite wall connection system allows nearly unrestrained in-planemovement of the two concrete layers. Thermal bow is minimized, and jointsealants are less likely to fail.

[0010] Each of the wall types therefore have positive and negativefeatures. Although non-composite wall panels are generally too flexibleor have insufficient strength to safely resist wind loads, manycomposite and partially composite wall panels have excess capacity andsuffer from thermal and differential prestress bowing. There is a needfor an intermediate, partially composite connection system for concretesandwich panels that provides adequate resistance to lateral loads whileproviding reduced thermal bowing and provides a thermally efficient wallpanel.

[0011] Prior art connecting systems generally include connectors made ofwire or polymers. Such connectors are usually narrow or slender, andtherefore have a low bending stiffness, which results in small sheartransfer between the concrete layers. Merely increasing the dimensionsor amount of material used in the prior art connectors is not asatisfactory solution. While such strategies will increase the strengthof the connectors, much of the excess material does not add to thestrength of the connector and is therefore wasted. Furthermore, suchenlarged connectors will tend to twist in the concrete layer andconsequently not develop the tension and compression forces at theextreme ends of the connectors that are necessary to ensure a transferof shear.

[0012] U.S. Pat. No. 5,440,845 describes a concrete sandwich wall panelincluding insulating connectors having opposite end portions embedded ina corresponding one of the concrete layers or wythes. The connectors arereferred to as two-way shear connectors and are capable of transferringlongitudinal shear loads from one wythe to the other in multiple or, inan alternative embodiment, in all directions. The concrete sandwichpanel wall is constructed so that the connectors are supported at theiropposite end portions on elongated strands that are embedded, one each,in the two wythes. A number of diverse configurations of the connectorsare described, including a strand, plurality of plate shaped connectors,I-shaped beams, and hinged or stapled straps. In all configurations,however, the connectors are functionally associated with the elongatedstrands to provide for the transmission of stresses between the wythesto accomplish the purposes of the assemblies as specified in the patent.

[0013] In contrast, the connectors of the present invention have nofunctional association with any elongated strands that may or may not bepresent in the concrete layers. While prestressing strands may be usedin some applications of concrete sandwich walls of the presentinvention, when present, no connection or association is made betweenthe prestressing strands and the insulating connectors. Rather, theconnectors of the present invention are designed to provide therequisite transmission of forces merely by being consolidated in theconcrete layers. The connectors of the present invention, therefore,provide more flexibility to the engineer or architect in designing theconcrete sandwich wall, are much quicker and easier to construct, and donot require as much skill to construct.

[0014] Therefore, a primary objective of the present invention is theprovision of an improved concrete sandwich wall panel that is stiff,strong and thermally efficient.

[0015] Another objective of the present invention is the provision of animproved connector for use in a concrete sandwich wall that develops endmoments to ensure the transfer of shear between the concrete layers inwhich the connectors are embedded.

[0016] A further objective of the present invention is the provision ofan improved connection system for concrete sandwich walls which allowsfor partial composite action.

[0017] Another objective of the present invention is the provision of aconnector for concrete sandwich walls having sufficient bendingstiffness to provide significant shear transfer between the two concretelayers when the panel is subjected to wind or seismic forces appliednormal to the plane of the panel.

[0018] Another objective of the present invention is the provision of awide-body connector for use in concrete sandwich wall panels that can beused either as curtain wall units or for carrying roof loads.

[0019] A further objective of the present invention is the provision ofconnectors for concrete sandwich walls, wherein each connector has apair of spaced apart, longitudinally extending flanges interconnected bya web to provide enhanced performance for the wall panel.

[0020] Still another objective of the present invention is the provisionof a connection system for concrete sandwich walls which reduces thethickness of the concrete layers and minimizes the number of connectors.

[0021] A further object of the present invention is the provision of aconnection system for concrete sandwich walls that require less skilland are faster and less expensive to construct.

[0022] These and other objectives will become apparent from thefollowing description of the invention.

BRIEF SUMMARY OF THE INVENTION

[0023] The connectors of the present invention are formed of a thermallyinsulative material, such as fiber-reinforced polymer, and are intendedfor use in a concrete sandwich wall having spaced apart layers ofconcrete with an insulation layer sandwiched therebetween. Eachconnector includes an elongated body that extends through the insulationlayer and opposite ends that extend into the respective concrete layers.Anchoring surfaces are provided in the opposite ends to facilitateanchorage of the connector in the concrete and to develop end moments toassist in the transfer of shear between the layers of concrete. Theconnectors are not attached to or functionally associated with anreinforcing members or elongated strands that may be present in theconcrete layers.

[0024] The body of each connector has a width that is typically twicethe thickness of the body. The body includes longitudinally extendingthickened portions that define longitudinally extending flanges that areinterconnected by a thinner central web. The flanges and web providebending stiffness for the connector and enhance shear transfer betweenthe concrete layers. Each connector preferably includes a lip extendingpartially or fully around the body so as to limit penetration of theconnector through the insulation layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a perspective view of a first embodiment of thewide-body connector of the present invention.

[0026]FIG. 2 is a partial sectional view through a concrete sandwichwall panel showing one of the connectors in place.

[0027]FIG. 3 is a sectional view taken along lines 3-3 of FIG. 1.

[0028] FIGS. 4-8 are perspective views showing alternative embodimentsof wide-body connectors of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0029] A first embodiment of the wide-body connector of the presentinvention is generally designated by the reference numeral 10 in FIGS.1-3. The connector 10 is intended for use in a concrete sandwich wall 12having a first concrete layer 14, a second concrete layer 16 and aninsulation layer 18 sandwiched therebetween.

[0030] The connectors 10 are made of high R-value material, so as toeliminate or minimize thermal transfer between the concrete layers.

[0031] The connector 10 includes an elongated body 20 having oppositeends 22, 24. As seen in FIGS. 1 and 3, the width of the body 20 ispreferably at least 4-6 times the thickness of the body 20. The body 20includes spaced apart thickened portions that run the length of the body20. These thickened portions generally define flanges 26 that enhancethe bending stiffness of the connector 10. The flanges 26 areinterconnected by a thinner central portion or web 28.

[0032] A lip 30 is provided on the body 20 and functions to limit thepenetration of the body 20 through the insulation layer 18 by engagingthe surface of the insulation layer, as seen in FIG. 2. In a preferredconstruction process, the lip 30 is overmolded onto the body 20. The lipmay be part of an encasement 32 including ribs 34 that facilitateretention of the connector 10 in the insulation layer 18.

[0033] The body 20 also includes anchoring surfaces 36 adjacent each end22, 24, which enhance retention of the connector 10 in the concretelayers 14, 16. The anchoring surfaces 36 are formed into the body 20 inany convenient manner. In a preferred manufacturing process, the body 20is formed by pultrusion, and the anchoring surfaces 36 are cut or milledinto the body 20 after the polymer material has hardened. Materialspreferred for use in forming the connectors 10 and body 20 are fiberreinforced polymers, including glass-reinforced thermoset resins, suchas DEXRANE® epoxy vinyl resin (Dow Chemical).

[0034] The connectors 10 are installed in the wall panel 12 in aconventional manner, with corresponding slots or holes pre-cut or formedin the insulation layer 18 at the appropriate locations. Generally, thefirst concrete layer 14 is poured and the insulation layer 18 withpreformed holes therein is set on top of the concrete layer 14. Theconnectors 10 are then pushed through the preformed holes in theinsulation layer 18 until the lip 30 engages the insulation layer 18.Alternatively, the insulation layer 18 may in the form of strips thatare placed at the preferred spacing corresponding to the positioning ofthe connectors 10 which are then pushed through the strips of insulationat the predetermined spacing. Thus, the first end 22 of the connector 10is embedded in the first concrete layer 14, and the second end 24 of theconnector 10 extends above the insulation layer 18. The second concretelayer 16 is then poured on top of the insulation layer 18 so as to embedthe second end 24 of the connector 10 in the second concrete layer 16.The plasticity of the concrete layers allows the concrete to consolidatewith the anchoring surfaces 36, such that the connector 10 ties thefirst and second concrete layers 14, 16 together. The concrete may bevibrated to hasten consolidation.

[0035] In use, the increased bending stiffness provided by thelongitudinally extending flanges 26 allows the web 28 to provideenhanced shear transfer between the concrete layers 14, 16.Additionally, the anchoring surfaces 36 prevent or limit twisting of theend portions of the connectors 10 in the concrete layers 14, 16, thuspermitting the development of end moments, either positive or negative,on the ends of the connectors 10. The connectors 10, accordingly, areeffective at transferring shear between the concrete layers 14, 16 andso add to the composite characteristics of the concrete wall panel 12.Additionally, the connectors 10 allow for reduced-thickness concretelayers 14, 16 and/or a reduced number of connectors in the wall panel12.

[0036] FIGS. 4-8 show alternative embodiments of the connector withsimilar parts labeled with the same reference numerals, and the suffixis A-E. Thus, FIG. 4 shows a perspective view of a connector 10A withflanges 26A and an interconnecting web 28A. The lip 30A extends from oneside of the connector 10A, rather than 360° around the connector, asseen in the connector of FIGS. 1-3. The anchoring surfaces 36A of theconnector 10A are formed by a portion 38A overmolded on the ends of thebody 20A.

[0037]FIG. 5 shows a connector 10B with flanges 26B and aninterconnecting web 28B. The flanges 26B are spaced inwardly from theopposite sides of the body 20B. The lip 30B extends from one side of theconnector 10B, and the anchoring surfaces 36B are formed with anovermolded portion 38B.

[0038]FIG. 6 shows a connector 10C wherein the thickened portionsdefining the flanges 26C extend in opposite directions from the majorcross-sectional axis of the connector 10C. The flanges 26C areinterconnected by the thinner central web 28C. An overmolded portion 32Cincludes the lip 30C. Overmolded portions 38C define the anchoringsurfaces 36C.

[0039]FIG. 7 shows yet another embodiment of a connector 10D having abody 20D that is substantially similar to the body 20C of the connector10C shown in FIG. 6. The connector 10D does not include any overmoldedportions, as with the connector 10C. The flanges 26D are interconnectedby the web 28D, with anchoring surfaces 26D cut, milled or otherwiseformed in the body 20D.

[0040]FIG. 8 shows another embodiment of a connector 10E. The connector10E includes flanges 26E defined by C-shaped side portions. A thininterconnecting web 28E interconnects the flanges 26E. An encasement32E, having a lip or flange 30E and ribs 34E, is overmolded onto theconnector 10E, similar to the embodiment of FIG. 1. Overmolded portions38E at the upper and lower ends of the connector provide an anchoringsurface 36E for the connector. The ends 38E are rounded to facilitateinsertion of the connector into the uncured concrete. In the preferredmanufacturing process for connector embodiments A, B, C, and E, the body20 is again formed by pultrusion, but the anchoring surfaces 36 areovermolded onto the body 20 after the polymer material in the pultrudedpart has partially or completely solidified. Materials preferred for usein forming the connectors 10 and body 20 include fiber-reinforcedthermoplastic resins, such as ISOPLAST® resin (Dow Chemical). In thepreferred manufacturing process for connector 10D, the body 20D is againformed by pultrusion. Connector 10D can be conveniently formed usingthermoset resins with milled anchorage surfaces 36D, or usingthermoplastic resins with thermally-mechanically formed surfaces 36D.Finally, still another manufacturing process that may be used for any ofthe connector embodiments shown is to injection mold the connectorsusing a fiber-reinforced thermoplastic resin. Using this process, allsurface features of the connector are formed in a single process.

[0041] With the wide-body connectors of the present invention, aconcrete sandwich wall has a substantially composite nature, since theconnectors enhance the transfer of forces between the concrete layers,while also eliminating or minimizing thermal transfer or bridgingbetween the concrete layers.

[0042] The preferred embodiment of the present invention has been setforth in the drawings, specification, and although specific terms areemployed, these are used in a generic or descriptive sense only and arenot used for purposes of limitation. Changes in the form and proportionof parts as well as in the substitution of equivalents are contemplatedas circumstances may suggest or render expedient without departing fromthe spirit and scope of the invention as further defined in thefollowing claims.

What is claimed is:
 1. A connector for an insulated concrete wall havingspaced apart first and second layers of concrete and an insulation layersandwiched between the concrete layers comprising, an elongated bodyhaving opposite first and second ends and having laterally spaced apartand longitudinally extending flanges interconnected by a web.
 2. Theconnector of claim 1 wherein the body transfers forces between the firstand second concrete layers such that the wall is substantially compositein character.
 3. The connector of claim 1 further comprising first andsecond anchoring surfaces on the first and second ends adapted to anchorthe first and second ends in the first and second layers of concrete,respectively.
 4. The connector of claim 3 wherein the first and secondanchorage surfaces are capable of transferring tension and compressionforces along the flanges.
 5. The connector of claim 1 further comprisingan outwardly extending lip adapted to engage the insulation layer so asto limit the penetration of the connector through the insulation layer.6. The connector of claim 1 wherein the body comprises a polymermaterial.
 7. A wall panel, comprising: (a) spaced apart first and secondconcrete layers; (b) an insulation layer between the concrete layers;(c) a plurality of elongated connectors each extending through theinsulation layer and having opposite ends embedded in the concretelayers; and (d) each connector having longitudinally extending thickenedportions with a thinner web extending between the thickened portions. 8.The panel of claim 7 wherein the connectors transfer forces between thefirst and second concrete layers whereby the wall has a substantiallycomposite character.
 9. The wall panel of claim 7 wherein the thickenedportions and the web of each connector extend substantially along thelength of the connectors.
 10. The wall panel of claim 7 wherein thethickened portion of the connectors comprise an anchoring surfaceadjacent each end.
 11. The connector of claim 10 wherein the connectorshave first and second anchorage surfaces capable of transferring tensionand compression forces along and parallel to the longitudinally extendedthickened portions.
 12. The wall panel of claim 7 wherein each connectorhas a centrally located region comprising a lip extending outwardly toengage the insulation layer.
 13. The wall panel of claim 7 wherein eachconnector is made of a polymer material including fiber reinforcements.14. A connector for an insulated concrete wall having spaced apart firstand second layers of concrete and an insulation layer sandwiched betweenthe concrete layers, comprising an elongated body having a width and athickness, with the width being at least twice the thickness along thelength of the connector.
 15. The connector of claim 14 wherein the bodytransfers forces between the first and second concrete layers such thatthe wall is substantially composite in character.
 16. The connector ofclaim 14 wherein the body includes at least one longitudinally extendingflange.
 17. The connector of claim 14 wherein the body has a pair oflaterally spaced apart longitudinally extending flanges interconnectedby a web.
 18. The connector of claim 14 further comprising anchoringsurfaces at each end of the body to anchor the body in the concretelayers.
 19. The connector of claim 18 wherein the first and secondanchorage surfaces are capable of transferring tension and compressionforces along the flanges.
 20. The connector of claim 14 furthercomprising a lip on the body adapted to engage the insulation layer tolimit penetration of the body through the insulation layer.
 21. Theconnector of claim 6 wherein the polymer material is selected from thegroup comprising fiber-reinforced thermoplastic resin andfiber-reinforced thermoset resin.